Add US Only filter button for international students

src/pages/Index.tsx

@@ -105,6 +105,9 @@ const Index = () => {
     window.history.replaceState({}, '', `${window.location.pathname}?${searchParams}`);
   };
 
+  // Define US states and territories that should be included in "US Only" filter
+  const usRegions = new Set(["USA", "PENNSYLVANIA", "New Mexico", "Michigan", "Tennessee", "Hawaii"]);
+
   // Toggle a single tag
   const toggleTag = (tag: string) => {
     const newTags = new Set(selectedTags);
@@ -232,6 +235,25 @@ const Index = () => {
                 </PopoverContent>
               </Popover>
               
+              {/* US Only filter button */}
+              <Button 
+                variant={Array.from(selectedCountries).every(country => usRegions.has(country)) && selectedCountries.size > 0 ? "default" : "outline"}
+                size="sm" 
+                className="h-8 gap-1"
+                onClick={() => {
+                  const isUSOnlyActive = Array.from(selectedCountries).every(country => usRegions.has(country)) && selectedCountries.size > 0;
+                  if (isUSOnlyActive) {
+                    // If already filtering US only, clear the filter
+                    handleCountriesChange(new Set());
+                  } else {
+                    // Set filter to US only (all US regions)
+                    handleCountriesChange(usRegions);
+                  }
+                }}
+              >
+                🇺🇸 US Only
+              </Button>
+              
               {/* Display selected countries */}
               {Array.from(selectedCountries).map(country => (
                 <button