RUGBY, England—Stuart Field raised his first flags in July: the English red cross of St. George and also a smattering of the British red, white and blue, hanging them from his hometown’s streetlights.

The national flag of England, a white banner with a bold red cross, has been displayed by soccer fans during the World Cup. But it has caused tension over whom, and what, it is meant to represent. St.

Across England, flags are visible like never before. They are being hoisted on lamp-posts. Hastily painted representations of the St George’s flag, typically little more than a couple of red lines ...