Change default language to en-US and add US language (#6621)

frontend/editor/src/proprietary/components/shared/config/configSections/AdminGeneralSection.tsx

@@ -625,7 +625,7 @@ export default function AdminGeneralSection() {
                 data={defaultLocaleOptions}
                 searchable
                 clearable
-                placeholder="en_GB"
+                placeholder="en_US"
                 comboboxProps={{ zIndex: Z_INDEX_CONFIG_MODAL }}
                 disabled={!loginEnabled}
               />

frontend/editor/src/proprietary/routes/Login.test.tsx

@@ -26,10 +26,10 @@ vi.mock("react-i18next", () => ({
 // Mock i18n module to avoid initialization
 vi.mock("@app/i18n", () => ({
   updateSupportedLanguages: vi.fn(),
-  supportedLanguages: { "en-GB": "English" },
+  supportedLanguages: { "en-US": "English (US)" },
   rtlLanguages: [],
   default: {
-    language: "en-GB",
+    language: "en-US",
     changeLanguage: vi.fn(),
     options: {},
   },