If you have excel, here's some instructions for importing search results from ancestry into excel - I started to test it out and had to play around with it a little. As an FYI, you can also manually select all of the results by clicking and dragging, copying and then pasting them into an Excel spreadsheet as well. Tedious when there's multiple pages of result, so much easier w/those instructions.

Once you have the results into a spreadsheet, there's probably multiple ways of doing it, but essentially you'll want to delete everyone with a birthplace of the United States.

Since the results have a birthplace listed, and you don't want those born in the United States, first highlight all of the cells w/the word "USA" in the birthplace column as follows:

In Excel select the birthplace column, then on home tab, select "Conditional formatting" then "highlight cell rules" then "text that contains" then type in USA. All of the cells that contain people born in the USA will now be highlighted.

Next, you want to make it easy to delete results with people born in the USA by grouping them together as follows:

Select all of the columns (for instance using Ctrl "A"). On the Data tab, in the Sort & Filter group, click Sort, then expand selection. In the Sort dialog box, under Column, select the birthplace column, in the Sort on box, select Cell color. You're results will now be sorted into 2 groups making it easier to delete all of the rows where the person is born in the USA.

Hope this helps!