Fix doulbe/half prop problem in USAFacts this time
**Actual Behavior:**

Same bug as #325, in USAFacts this time

**Expected behavior**

State prop signals should incorporate 1x the state population (which requires ignoring the population of the megafips during county->state aggregation)

diff --git a/usafacts/delphi_usafacts/geo.py b/usafacts/delphi_usafacts/geo.py
index 53542a6c..5979a5e2 100644
--- a/usafacts/delphi_usafacts/geo.py
+++ b/usafacts/delphi_usafacts/geo.py
@@ -107,6 +107,13 @@ def geo_map(df: pd.DataFrame, geo_res: str, map_df: pd.DataFrame, sensor: str):
         df = df.append(unassigned_counties)
         geo_mapper = GeoMapper()
         df = geo_mapper.add_geocode(df, "fips", "state_id", new_col="geo_id")
+
+        # Zero out the state FIPS population to avoid double counting.
+        df = df.set_index("fips")
+        state_fips_codes = {str(x).zfill(2) + "000" for x in range(1, 73)}
+        subset_state_fips_codes = set(df.index.values) & state_fips_codes
+        df.loc[subset_state_fips_codes, "population"] = 0
+        df = df.reset_index()
     elif geo_res in ("msa", "hrr"):
         # Map "missing" secondary FIPS to those that are in our canonical set
         for fips, fips_list in SECONDARY_FIPS:
diff --git a/usafacts/tests/test_geo.py b/usafacts/tests/test_geo.py
index 33fe7dd3..c6f52a1a 100644
--- a/usafacts/tests/test_geo.py
+++ b/usafacts/tests/test_geo.py
@@ -76,11 +76,11 @@ class TestGeoMap:
         """Tests that values are correctly aggregated at the state level."""
         df = pd.DataFrame(
             {
-                "fips": ["04001", "04003", "04009", "25023"],
-                "timestamp": ["2020-02-15", "2020-02-15", "2020-02-15", "2020-02-15"],
-                "new_counts": [10, 15, 2, 13],
-                "cumulative_counts": [100, 20, 45, 60],
-                "population": [100, 2100, 300, 25],
+                "fips": ["04001", "04003", "04009", "25023", "25000"],
+                "timestamp": ["2020-02-15", "2020-02-15", "2020-02-15", "2020-02-15", "2020-02-15"],
+                "new_counts": [10, 15, 2, 13, 0],
+                "cumulative_counts": [100, 20, 45, 60, 0],
+                "population": [100, 2100, 300, 25, 25],
             }
         )
 
['usafacts/tests/test_geo.py', 'usafacts/delphi_usafacts/geo.py']