import re
texts = ["Mark Samson: CA", "Sam Smith: US", "Dawn Watterton: CA", "Neil Shughar: CA", "Fennial Fontaine: US"]
for text in texts:
match = re.search(r".+?(?=:\s*US$)", text)
if match:
print(match.group())
aW1wb3J0IHJlCnRleHRzID0gWyJNYXJrIFNhbXNvbjogQ0EiLCAiU2FtIFNtaXRoOiBVUyIsICJEYXduIFdhdHRlcnRvbjogQ0EiLCAiTmVpbCBTaHVnaGFyOiBDQSIsICJGZW5uaWFsIEZvbnRhaW5lOiBVUyJdCmZvciB0ZXh0IGluIHRleHRzOgoJbWF0Y2ggPSByZS5zZWFyY2gociIuKz8oPz06XHMqVVMkKSIsIHRleHQpCglpZiBtYXRjaDoKCQlwcmludChtYXRjaC5ncm91cCgpKQ==