locale errors everywhere. Help.

Hi all. Yesterday I did set up a linux headless server, but after doing so, something seems to have messed up. I have this error when I try to open a man page:
man: can't set the locale; make sure $LC_* and $LANG are correct
locale reports: LANG=en_US.UTF-8
LANGUAGE=en_US:en
LC_CTYPE="en_US.UTF-8"
LC_NUMERIC=nl_NL.UTF-8
LC_TIME=nl_NL.UTF-8
LC_COLLATE="en_US.UTF-8"
LC_MONETARY=nl_NL.UTF-8
LC_MESSAGES="en_US.UTF-8"
LC_PAPER=nl_NL.UTF-8
LC_NAME=nl_NL.UTF-8
LC_ADDRESS=nl_NL.UTF-8
LC_TELEPHONE=nl_NL.UTF-8
LC_MEASUREMENT=nl_NL.UTF-8
LC_IDENTIFICATION=nl_NL.UTF-8
LC_ALL=
sudo dpkg-reconfigure locales gives:
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
LANGUAGE = "en_US:en",

LC_ALL = (unset),

LC_PAPER = "nl_NL.UTF-8",

LC_ADDRESS = "nl_NL.UTF-8",

LC_MONETARY = "nl_NL.UTF-8",

LC_NUMERIC = "nl_NL.UTF-8",

LC_TELEPHONE = "nl_NL.UTF-8",

LC_IDENTIFICATION = "nl_NL.UTF-8",

LC_MEASUREMENT = "nl_NL.UTF-8",

LC_all = "en_US.UTF-8",

LC_TIME = "nl_NL.UTF-8",

LC_NAME = "nl_NL.UTF-8",

LANG = "en_US.UTF-8"

are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").
locale: Cannot set LC_ALL to default locale: No such file or directory
Generating locales...
en_AG.UTF-8... up-to-date
en_AU.UTF-8... up-to-date
en_BW.UTF-8... up-to-date
en_CA.UTF-8... up-to-date
en_DK.UTF-8... up-to-date
en_GB.UTF-8... up-to-date
en_HK.UTF-8... up-to-date
en_IE.UTF-8... up-to-date
en_IN.UTF-8... up-to-date
en_NG.UTF-8... up-to-date
en_NZ.UTF-8... up-to-date
en_PH.UTF-8... up-to-date
en_SG.UTF-8... up-to-date
en_US.ISO-8859-1... up-to-date
en_US.UTF-8... up-to-date
en_ZA.UTF-8... up-to-date
en_ZM.UTF-8... up-to-date
en_ZW.UTF-8... up-to-date
Generation complete.
More errors, I'm not sure where they are coming from.
Anyone who can help me? I've searched the internet all over, and I can just not find a solution. So yes, I did try the search function.

Greetings,
Jelmer

could u show the output of

Code:

---

cat /etc/default/locale

---

LANG=en_US.UTF-8
LANGUAGE="en_US:en"

try

Code:

---

sudo locale-gen nl_NL.UTF-8

---