Some do, most don’t. There are a lot of additional legal issues to an American investor putting his/her money into a company in another country. There’s also the fact that the big-name deal flow (Uber, Facebook, Workday, etc.) of the last 10 years has been concentrated in the U.S., which makes it harder for international startups to raise from U.S. investors.
That said, there are some, like Dave McClure/500 Startups with a more global approach to investing. You need to look for tech investors with a history of investing in other countries. They have already figured out the legal issues.