As do US employees and officers of foreign companies. The question is, how do we prevent that foreign influence on US elections? Merely repealing the 17th Amendment isn't going to change that. It would simply shift the money to other politicians. Prohibiting contributions from non-constituents would at least narrow the source of contributions significantly.
Does that include the national parties? I would allow any American citizen to donate any amount they want as individuals to candidates or parties -- no money from corporations, unions or PACs --- to anyone they want as long as there is full, 100% disclosure. I would also make contributions, up to a total of say $500, a full tax credit (not just a simple deduction) and end any and all Federal matching funds.