assignment with datetime64[ns, UTC] raises TypeError
#### Code Sample

```python
# Your code here

import datetime, pandas as pd

data = [[datetime.datetime(2020, 2, 28, 13, 51, 27, tzinfo=datetime.timezone.utc)],
 [datetime.datetime(2020, 2, 28, 13, 51, 27, tzinfo=datetime.timezone.utc)],
 [datetime.datetime(2020, 2, 28, 13, 51, 27, tzinfo=datetime.timezone.utc)],
 [datetime.datetime(2020, 2, 28, 13, 51, 27, tzinfo=datetime.timezone.utc)]]
df = pd.DataFrame(data, columns=['cd'])     # dtype: datetime64[ns, UTC]
df2 = pd.DataFrame(index=df.index)

df2.loc[:,'cd2'] = df['cd']                  # no error
df2.loc[df.index,'cd3'] = df['cd']     # error
df2.loc[df.index,'cd2'] = df['cd']     # no error

```
####  Problem description 

If you try to assign datetime values (with zone and indexes) to a column, it will raise TypeError: data type not understood. 
No errors raise with index ':', or when the column already has the correct type. Note that this only happens if the datetime has zone information. With tzinfo=None, no errors occur.

#### Output of ``pd.show_versions()``

I noticed this bug in version 1.0.1
No errors occur in 0.25.3

INSTALLED VERSIONS
------------------
commit           : None
pandas           : 1.0.1
numpy            : 1.16.4
pytz             : 2019.1
dateutil         : 2.8.0
pip              : 20.0.1
setuptools       : 45.1.0
Cython           : None
pytest           : None
hypothesis       : None
sphinx           : 2.4.2
blosc            : None
feather          : None
xlsxwriter       : None
lxml.etree       : None
html5lib         : None
pymysql          : None
psycopg2         : 2.8.2 (dt dec pq3 ext lo64)
jinja2           : 2.10.1
IPython          : 7.8.0
pandas_datareader: None
bs4              : 4.8.2
bottleneck       : None
fastparquet      : None
gcsfs            : 0.6.0
lxml.etree       : None
matplotlib       : 3.1.0
numexpr          : None
odfpy            : None
openpyxl         : None
pandas_gbq       : None
pyarrow          : 0.16.0
pytables         : None
pytest           : None
pyxlsb           : None
s3fs             : None
scipy            : 1.2.0
sqlalchemy       : None
tables           : None
tabulate         : None
xarray           : None
xlrd             : None
xlwt             : None
xlsxwriter       : None
numba            : None