If Iran attacks Israel, it would be absolutely irrational and counterproductive for US to start war with Iran.
Beyond military challenges, here are some of the economic and political consequences of the US-Iran war, with Iran closing the Straight of Hormuz (20% of the world’s oil) and Straight of Bab-el-Mandeb (12% of global trade):
1) Inflation. Gasoline prices will go up. Food prices will go up as well, because agriculture uses fertilizers that are made out of oil and transportation costs from rural areas to cities will increase substantially. Industrial products will become more expensive, because they contain products of petrochemical industry and because of high transportation costs. Price of transportation by truck, airplane and ship will increase and this will add to inflation. Standard of living of Americans will decrease, because of rising prices.
2) Exports from US to Europe and Asia will decrease, because there will be a recession in those regions. Imported goods will become more expensive adding to inflation in US.
3) Recession in the US. Falling exports on the one hand and less consumers spending because of high inflation on the other, will result in recession in US. US GDP will shrink 4-7%. If US and EU GDP shrinks by 6% that means US+EU GDP will shrink by 3trln$.
4) Unemployment. If US+EU unemployment increases by additional 6% due to recession, that means additional 20mln unemployed people in Europe and US. For comparison entire Iran’s labor force is 28mln people.
5) Stock Market Crash. Recession and worsening economic conditions will result in the crash of the stock market. Total market capitalization of the U.S. stock market is 50trln$ and EU’s stock market capitalization is 20trln$. If stocks value falls by 30% that is 21trln$ loss of wealth.
6) Bond Market Crash. If you hold US Treasures or US corporate bonds that pay 1% interest in times when inflation is 10-15% you will start selling your bonds and there will be crash in the bond market.
7) Financial Crisis. With the Crash of the Stock Market and Crash of the Bond Market banks will fail. Pension Funds, Investment Funds and Insurance companies might go bankrupt.
8) Budgetary Crisis in the US. With falling GDP you will have falling tax revenues and with rising unemployment and foreign war you will have rising spendings and budget deficit. With mass US Treasures sell-off by investors and foreign Central Banks, the cost of borrowing for US government will increase dramatically and this will be the road towards bankruptcy. And if the Fed starts printing money in these circumstances - this will be the end of dollar as a global reserve currency.
9) Political crisis in the US. American people will want someone to answer for this disaster and President Biden and his Jewish Secretary of State Blinken will become scapegoats and will be put on trial for causing this disaster.
10) Rise in Anti-Semitism in the US. When standard of living of Americans falls and unemployment increases, Americans will start questioning their support of Israel. Americans will ask why they have to fight and die because of Apartheid regime in Israel while paying high price of gasoline. You can see the rise of anti-Israeli and anti-Semitic sentiments among Americans.
11) Crisis in relations between the US and Europe. There might be crisis in relations between the US and their European clients. European elites will say that American policy in Ukraine resulted in war and left Europe without Russian oil and gas, and now American policy in the Middle East left Europe without Middle Eastern oil (20% of Europe’s demand) and gas. Europeans will say that Americans are to blame for economic crisis in Europe.
12) Rise in Anti-Americanism and Anti-Semitism in Europe (and in the world). There will be rise of anti-Americanism and anti-Semitism in Europe if there is economic crisis and massive unemployment, and falling standard of living in Europe because of US attacking Iran for the purpose of protecting Israel. Europe will be the biggest loser in the event of war, because after they were left without Russian oil and gas, they will be left without Middle Eastern oil, which is 20% of their demand and without 2trln$ trade with Asia via Bab-el-Mandeb Straight.
13) Political Crisis in Europe. If there is economic crises and falling standard of living, European populations will blame their leaders for their short-sighted policies of blindly following Americans that led to this disaster. You can see rise in popularity of alternative political parties in Europe like AfD in Germany for example.
14) Rise in Anti-Americanism in the Islamic World and more terrorist attacks against Westerners. Of course, if US fights 5 Muslim states simultaneously (Iran, Iraq, Syria, Lebanon, Yemen) on the side of Jews and against Palestinians, there will be huge rise of anti-Americanism in the Muslim world, more terrorist attacks against Westerners, and fully poisoned relations between the West and the World of Islam.
15) Military Crisis in East Asia. If Straight of Hormuz is closed, oil price increased and China experiences economic depression with huge unemployment, China will attack Taiwan for the purpose of diverting attention of domestic public from internal economic problems to external issues and finally solving the Taiwan problem. China will take advantage of the fact that US military will be bogged down in the Middle East and will not be in position to protect Taiwan. While invading Taiwan is not a military option at this moment, China can impose a naval blockade of the island and you will have a military crisis in East Asia. This shows how US attack on Iran and global economic depression can provoke a military crisis in East Asia.
16) 250$ oil price for Russia and Vladimir Putin. Of course, the biggest winner of US-Iran war and disruption of oil supply from the Persian Gulf will be Russia. A) Russia will be able to sell its oil at 250$ per barrel and earn a lot of money to fund its war in Ukraine and improve domestic economy B) Russia will be happy that US is in economic crisis and is militarily bogged down in the Middle East, while Europe is in economic and political crisis and is more dependent on Russian energy than before C) Russia might offer Europe to sell energy in exchange for Europe decreasing military support to Ukraine D) In times of global depression China will not be afraid of US sanctions and might start supplying weapons to Russia and helping it in its efforts in Ukraine in exchange for Russian energy. So Russia will be the only winner of another Gulf War if it happens.
All this shows that US starting war with Iran because of Israel will have catastrophic consequences for the West.
