Does International Cooperation Benefit The United States of America?

U.S. government space spending, which makes up more than 80 percent of global government space budgets

according to Government Budgets on the Space Foundation Web Site.

The US government spends four times as much on space as ALL the other governments combined.

This raises the question - Why are doing international cooperation?

It is usually claimed that the US can't afford to go it alone in space. This can't possibly be true since the United States Government is spending 80 percent of the of global government spending on space. The last 20% can't possibly make or break any project since much of that money must be spent just doing the basics such as having an office and nurturing local industry.

With the road block of ITAR (International Traffic in Arms Regulations) making it expensive and legally dangerous to do international aerospace trade, and all the cost of coordination, International Cooperation can not possibly be less expensive than purely American projects.

While I can see value in rewarding our Allies by allowing them to participate in our space activities off the critical path. I don't see how putting any partner on the critical path benefits any US space project.

Does the United States really benefit from international cooperation or is it just an excuse for government officials to travel abroad on the U.S. taxpayers dime?