But it looks like they may have servers there in Canada, or perhaps they incorporated there, but the Better Business Bureau says they are located in Arlington, VA 22219.
Can't really find out what the connection to Canada actually is.
I called (888) 288-1890, but no one answering the phone is the kind of person that has the answer as to their connection to Canada.
USPS snail mail - check or money order:
Donald J. Trump for President, Inc.
P. O. Box 13570
Arlington, VA 22219
Donations sent there, are processed with relative speed (usually within 1 week), by WinRed.
Donations to other locations mentioned by the Republican, and/or Trump campaigns, and/or House and Senate campaigns, may take weeks to be processed.
WinRed domain and website online info:
https://www.wmtips.com/tools/info/winred.com
https://dnslytics.com/domain/winred.com
WinRed his hosted by Cloudflare; e-mail MX record is Google.