For each investment in an AngelList syndicate deal, investors become members in a Delaware series LP. Each syndicate will send out the U.S. tax form K-1 to all its members, both foreign and domestic, in any year in which it has taxable income or deductible expenses.
This should not be construed as tax advice and you should consult your own tax advisors: that said, typical distributions for exit events from AngelList syndicated deals to non-US investors who don't meet US presence tests are not subject US tax and withholding requirements, provided that such investors have submitted the appropriate withholding forms.
There are important exceptions to the generalization stated above (including certain withholding requirements for non-exempt foreign entities under FATCA and relatively uncommon types of distributions to all types of foreign investors for interest, dividends and distributions that are effectively connected with a U.S. trade or business ), so please be sure to consult your tax advisor before making an investment.