In general:

Yankee (Americans) stands for business acumen, enterprise, pioneering spirit and behavior with which we successfully realized our purposes, but it is also urged to take a little more consideration of others needs.

Traditionally:

European
– To see yankee or communicate with him (or them – Yankees): means that dreamer can expand his business to advantage; promises a success; promises and obligations you will be faithful;
– Also dreaming of yankee: renewed friendship with someone, with whom you has been separated long time ago.